WidgetCell & LiveWidgetPreview cleanup am: ae6b34811b

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/13790508

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I8f8304fcc662286b6e61a4646cfd2e0bc22e9016